A Manhattan high-school teacher, suspended after admitting he sent sexually explicit e-mails to a 16-year-old female student, can return to the classroom next year, an arbitrator has ruled.

Cary Hershkowitz, 52, can keep his $70,000-a- year job as a chemistry teacher at Health Professions and Human Services HS, even though he asked the girl if she “would want to have sex; both with others and me,” according to a recent decision obtained by The Post.

The ruling, five years in the making, was made on the grounds that Hershkowitz was never offered union representation when investigators questioned him – a claim the city Department of Education denies.

Schools Chancellor Joel Klein said he would not allow Hershkowitz to return to the classroom.

“This is yet another glaring example of how dysfunctional the current process for terminating employees is,” Klein said. “Is there anyone in our city who would want this teacher back in the schools with children?”

Hershkowitz has been suspended with pay from the Lower East Side school since May 1999, when his arbitration hearing began. Under the latest decision, he is suspended without pay until he returns next year.

“Considering the severity of [his] offense . . . and the mitigating factor of his 25 years of service,” hearing officer Robert Simmelkjaer wrote, “a one-year suspension without pay is the appropriate penalty.”

Simmelkjaer threw out the case against Hershkowitz altogether in 2000 because there was no evidence the teacher was offered a union rep. A state Supreme Court judge overturned that decision.

In a handwritten confession Hershkowitz made in June 1998, he admitted asking the girl for sex, questioning whether “she ever did it,” and whether she “explored her own body.”

He also admitted discussing oral sex in the messages.

Many of the Internet messages took place between January and June 1998. The girl used the alias “CUTEE 101,” while Hershkowitz went under “IB4UALONE,” according to court documents.

School officials learned of the illicit relationship from the girl’s mother, who complained that Hershkowitz had called their house. He admitted to making the calls, saying he wanted “to be reminded of [the girl’s] voice” and save time on the computer.

Hershkowitz could not be reached at his Rockland County home. His mother, who answered the phone, declined to comment.

In his confession, Hershkowitz said, “This is an isolated case which spiraled out of control and I always had the plan never to . . . hurt anyone.”

No one from the United Federation of Teachers returned phone calls, but union president Randi Weingarten has said she favors reforming the disciplinary process in certain circumstances.

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Sex education

From the signed confession of Cary Hershkowitz:

“Some of the messages did get into specifics concerning a future sexual relationship . . . including the idea of oral sex, talking about, ‘if she ever did it’ or ‘explored her own body,’ and if we could touch each other if we got together.”

“I had asked . . . whether she would want to have sex; both with others and me.”